This invention relates to a motorcycle and more particularly to an improved suspension and driving arrangement for the driven wheel of a motorcycle or motorcycle type of vehicle.
As is well known, motorcycles embody a frame assembly upon which an engine is mounted. In conventional motorcycle practice, the engine crankcase has built into it an integral change speed transmission. This change speed transmission drives the rear wheel through a driving arrangement, quite frequently a chain or the like. The rear wheel, however, is suspended for movement relative to the frame generally by a trailing arm suspension. Thus, the driven wheel will move in an arc relative to the output shaft of the transmission and this can give rise to certain problems, particularly if the pivot axis of the rear wheel suspension is offset to any great degree from the output shaft axis of the transmission.
In order to minimize the difference in chain length as occurs during the suspension movement, it has been proposed to align the transmission output shaft axis with the pivot axis for the rear wheel suspension arm. This, however, gives rise to a number of problems. Specifically, it is quite difficult to position all of the components in a manner so that a compact construction, as is necessary with a motorcycle, can be provided. For example, it has been proposed to use a co-axial arrangement wherein the pivot shaft and output shaft are telescoped one within the other. However, when this is done, then the output shaft tends to become large in diameter to transfer the necessary driving forces and, accordingly, the sprocket wheel or drive element that is affixed to the output shaft also may become large. This causes a number of problems one of which is that it adversely effects the drive ratio between the engine output shaft and the rear wheel since the large sprocket limits the attainable ratios. In addition, it is necessary to provide seals between the respective shafts, particularly in the area where the transmission output shaft passes through the transmission case. Also, it is then necessary to disassemble the entire rear wheel suspension in order to service the driving chain and/or sprocket.
It is a principal object of this invention to provide an improved compact suspension and drive arrangement for a motorcycle rear wheel that is relatively insensitive to suspension travel.
It is, another object of this invention to provide an improved driving and rear suspension arrangement for a motorcycle type of vehicle wherein the pivot axis of the rear wheel suspension and the pivot axis of the transmission shaft are closely positioned to each other but are not directly aligned.
It is a further object of this invention to provide an improved suspension and drive arrangement for a motorcycle rear wheel wherein the driving sprocket for the rear wheel drive can be serviced without necessitating disassembly of the suspension or any components of it.